The present invention, which is a CIP of 07/692,006 filed Apr. 26, 1991, now abandoned, relates to a photomask with pellicle used in a photolithographic process in the manufacture of semiconductor products, precision electronic parts, etc. and also relates to a method of treating and storing the same.
Hitherto, photomasks employed in the manufacture of semiconductor products and the like have been produced by various methods and used for patterning of semiconductor products, precision electronic parts, etc. In many cases, such photomasks are used repeatedly, and it is conventional practice to clean each photomask after production and to use it as it is or with a pellicle attached thereto for protection. To store or transport the photomask, it is put in a casing after being cleaned, and in this state it is stored or transported.
Since a photomask has heretofore been cleaned after production and then stored or transported in a casing as it is or with a pellicle attached thereto, as stated above, it is likely that the water content in the air and a low-volatile component contained in the casing and pellicle materials will adhere to contaminative particles attached to the obverse and reverse surfaces of the photomask in a trace amount during or after the cleaning process and the resulting stain will gradually grow with such particles at their centers, thus making an adverse effect on the pattern printing process. For this reason, it has been difficult to store photomasks for a long period of time. In particular, a photomask used for projection exposure, not for contact exposure, is frequently used with a pellicle attached thereto for protecting the surface of the photomask. Therefore, it is necessary to detach the pellicle in order to remove the stain grown on the obverse surface of the mask within the pellicle and on the reverse surface thereof as described above, which is uneconomical in terms of cost and labor. In addition, the photomask itself is likely to be damaged. Accordingly, it is practically difficult to remove such stain by cleaning process. Thus, it has heretofore been difficult to store such photomasks for a long period of time.